docs: def addFeatureStartLocation(
              self, coordinate, reference_id, strand=None, position_types=None):
          """
          Adds coordinate details for the start of this feature.
          :param coordinate:
          :param reference_id:
          :param strand:
          :param position_types:
  
          :return:
  
          """
  
          # make an object for the start, which has:
          # {coordinate : integer, reference : reference_id, types = []}
          self.start = self._getLocation(coordinate, reference_id, strand, position_types)
  
          return